Climate change and continuous demographic growth is putting an unprecedented burden on growers to meet food demand while reducing water consumption. The industry has the difficult challenge of feeding 9 billion people by 2050 with less water. The situation is already critical in California, which is experiencing an exceptional drought, even while providing more than 50% of US grown fruits, nuts and vegetables. For specialty crops including almonds, California grows more than 90% of the supply.
Growers now have access to a range of irrigation techniques and monitoring sensors to respond to conserve water and increase yield. Drip irrigation is very popular for specialty crops such as almonds and grapes in California. Center pivots are widely deployed in areas of the Mid West to increase yield of annual crops such as corn and wheat, which relied mostly on rain before. The most common irrigation method still remains surface irrigation. More than 70% of farmed lands in the world use flood or furrow irrigation. Their irrigation efficiency is low, typically 70-80% compared to 85-95% for drip irrigation.
Poor irrigation efficiency comes from lack of uniformity in the distribution of water over the field, and also from variability in soil water holding capacity. By investing in data acquisition such as soil samples and soil sensors, and by hiring crop advisors and irrigation specialists to interpret those, growers can adopt more effective farming practices. Data acquisition and analysis, however, remain very labor intensive.
Irrigation uniformity is commonly measured by a standard distribution uniformity (DU) test. An array of cups measures the amount of water at different locations on a field, and the recorded data are manually recorded. An example of DU test is shown in FIG. 1. A DU test is a very good indicator of the efficiency of the irrigation infrastructure. DU is defined as the average of the lowest quartile on the field divided by the average across the field. An example is provided in FIG. 2.
      Distribution    ⁢                  ⁢    Uniformity    =            water      ⁢                          ⁢      applied      ⁢                          ⁢      to      ⁢                          ⁢      driest      ⁢                          ⁢      25      ⁢      %              average      ⁢                          ⁢      amount      ⁢                          ⁢      of      ⁢                          ⁢      water      ⁢                          ⁢      applied      
DU tests are labor intensive and cost thousands of dollars. As a result, most farms can't afford it or will only measure part of a field that they know have a problem. It is not uncommon for two thirds of the revenue to come from one third of the farmed land.
Soil variability is also an important factor. Soils vary in their composition of sand, clay and silt. As a result, they have different water holding capacity. The various types of soils are summarized in the textural triangle provided by the National Conservation Resource Services (NRCS) at the US Department of Agriculture (FIG. 3). NRCS actually generated soil maps several decades ago and makes them available for free on its web soil survey portal. An example of USDA soil map is in FIG. 4. However, the maps are often outdated due to erosion, tillage, etc. Most farms don't rely on them to make decisions. Moreover, the maps were not generated using GPS technology and can be off by 100 feet.
One common technique to map the type of soil in a field is an electrical conductivity test. Sand, silt and clay have different conductivity properties as depicted in FIG. 5. Machines can be rented to generate a precise map. An example of machine pulled by a car is given in FIG. 6. A crop advisor will interpret it to provide a map and recommendations.